This is just one ISP to check out. click here
It may be advisable to inform your chosen ISP that the service is being used from a school, if this is indeed the case.
One thing is certain and that is security software must be installed before going online. You can get a recommended free anti-virus utility and a firewall from these links: click here and click here Other free anti-spyware utilities are mentioned in this forum and are well recommended to install. All security items must be kept updated to maintain best effectiveness.
Finally, never leave the computer running unattended with the dial-up modem connected to the Internet. Always disconnect when not required. TC.